MTC recommends there be .100-.125" clearance between the flat surface of the arms and the hardened steel buttons in the pressure plate.

Having too little clearance can result in the arms not  be able to swing out far enough to generate sufficient leverage to lock the clutch up.

Too much clearance especially on a multistage lockup results in the arm reaching its travel limit before applying enough force to lock up the clutch pack.

The .125" max is not as critical on the 2-stage lockup since these arms are capable of more travel than the multistage. In order to measure this clearance on a two stage lockup you will have to hold the arm in position.